Bicycle derailleur and method

Abstract

A front derailleur for use on devices such as bicycles is movable about a yaw axis while it moves laterally. The front derailleur may include a linkage in between a mount and a cage, with the linkage pivoting about two non-parallel axes. The front derailleur may include a linkage in between the mount and the cage that has links of different effective lengths. The front derailleur may include a single link and a cam.

What is claimed is: 
     
       1. A front derailleur for a bicycle having a frame member and a chain engaging one of a plurality of chainwheels, the frame member having a longitudinal axis, the front derailleur comprising:
 a mount configured to be fixed to the frame member; 
 a movable element separate from the mount and interiorly receiving a portion of the chain, the movable element contacting an exterior side of the chain to laterally displace the chain between the plurality of chainwheels; and 
 a linkage connecting the movable element to the mount and configured to move the movable element laterally with respect to the frame member and rotatably about a yaw axis substantially parallel to the longitudinal axis, wherein the movable element includes a cage having two side plates fixed relative to each other, the two side plates spaced apart from each other and interiorly receiving the portion of the chain therebetween, the side plates contacting the exterior side of the chain to laterally displace the chain between the plurality of chainwheels, and wherein the linkage includes a first link member connecting the cage to the mount and configured to move the cage laterally with respect to the frame member and rotatably about the yaw axis, the first link member being pivotally connected to the mount about a first pivot axis, and the first link member being pivotally connected to the cage about a second pivot axis, wherein the second pivot axis is at a first non-zero angle relative to the first pivot axis. 
 
     
     
       2. The front derailleur according to  claim 1 , wherein the frame member is a seat tube and the longitudinal axis is a central axis. 
     
     
       3. The front derailleur according to  claim 1 , further comprising:
 a second link member connecting the cage to the mount and configured to move the cage laterally with respect to the frame member and rotatably about the yaw axis, the second link member being pivotally connected to the mount about a third pivot axis, and the second link member being pivotally connected to the cage about a fourth pivot axis, wherein the fourth pivot axis is at a second non-zero angle relative to the third pivot axis, the first and second non-zero angles being equal. 
 
     
     
       4. The front derailleur according to  claim 3 , wherein the first and second non-zero angles are generally in the range of two to twenty degrees. 
     
     
       5. A front derailleur for a bicycle having a frame and a chain engaging one of a plurality of chainwheels, the front derailleur comprising:
 a mount configured to be fixed to the frame; 
 a movable element separate from the mount and interiorly receiving a portion of the chain, the movable element contacting an exterior side of the chain to displace the chain between the plurality of chainwheels; and 
 a linkage including a first link member connecting the movable element to the mount, the first link member being pivotally connected to the mount about a first pivot axis, and the first link member being pivotally connected to the movable element about a second pivot axis, wherein the second pivot axis is at a first non-zero angle relative to the first pivot axis. 
 
     
     
       6. The front derailleur according to  claim 5 , further comprising:
 a second link member connecting the movable element to the mount, the second link member being pivotally connected to the mount about a third pivot axis, and the second link member being pivotally connected to the movable element about a fourth pivot axis, wherein the fourth pivot axis is at a second non-zero angle relative to the third pivot axis, the first and second non-zero angles being equal. 
 
     
     
       7. The front derailleur according to  claim 6 , wherein the first and second non-zero angles are generally in the range of two to twenty degrees. 
     
     
       8. The front derailleur according to  claim 7 , wherein the movable element includes a cage having two side plates fixed relative to each other, the two side plates spaced apart from each other and interiorly receiving the portion of the chain therebetween, the side plates contacting the exterior side of the chain to laterally displace the chain between the plurality of chainwheels. 
     
     
       9. A front derailleur for a bicycle having a frame and a chain engaging one of a plurality of front chainwheels having a front chainwheel axis and engaging one of a plurality of rear chainwheels having a rear chainwheel axis, the front derailleur comprising:
 a mount configured to be fixed to the frame; 
 a movable element separate from the mount and having front and rear ends, the front end being farther from the rear chainwheels than the rear end, the movable element interiorly receiving a portion of the chain, the movable element contacting an exterior side of the chain to laterally displace the chain between the plurality of front chainwheels; and 
 a linkage connecting the movable element to the mount and configured to move the movable element from a first position to a second position relative to a plane perpendicular to the front chainwheel axis, the front end of the movable element moving a first distance from the first position to the second position relative to the plane, the rear end of the movable element moving a second distance from the first position to the second position relative to the plane, the first and second distances being unequal to each other, wherein the movable element includes a cage having two side plates fixed relative to each other, the two side plates spaced apart from each other and interiorly receiving the portion of the chain therebetween, the side plates contacting the exterior side of the chain to laterally displace the chain between the plurality of chainwheels, the front and rear ends being on the cage and wherein the linkage includes a first link member connecting the cage to the mount, the first link member being pivotally connected to the mount about a first pivot axis, and the first link member being pivotally connected to the cage about a second pivot axis, wherein the second pivot axis is at a first non-zero angle relative to the first pivot axis. 
 
     
     
       10. The front derailleur according to  claim 9  wherein the first distance is greater than the second distance. 
     
     
       11. The front derailleur according to  claim 9 , further comprising:
 a second link member connecting the cage to the mount, the second link member being pivotally connected to the mount about a third pivot axis, and the second link member being pivotally connected to the cage about a fourth pivot axis, wherein the fourth pivot axis is at a second non-zero angle relative to the third pivot axis, the first and second non-zero angles being equal. 
 
     
     
       12. The front derailleur according to  claim 11 , wherein the first and second non-zero angles are generally in the range of two to twenty degrees.